Dynamo-cooling system



Oct. 28, 1930. F. G. BAUM DYNAMQCOOLING SYSTEM Filed May 18, 1927 2Sheets-Sheet l ATTORN EY INVENTOR ATTORNEY 2 Sheets-Sheet 2 F. G. BAUMFiled May 18, 1927 DYNAMO COOLI NG SYSTEM Oct. 2s, 1930.

Patented Oct. 28, 1930 UNITED STATES PATENT OFFICE DYNAMo-cooLING SYSTEMApplication filed May 18, 1327'. Serial My invention relates'todynamo-electric machinery of the rotating pattern and particularly tomeans for the more effective cooling thereof.

The translation .of electrical energy from form to forni and from pointto point is never accomplished without some loss, and the lost energyappears at the site of translation as heat. The limitation upon thecapacity of any dynamo-electric machine accordingly is found to be therate at which the heat produced by the energy loss can be removed fromthe machine. Transformer devices are customarily cooled for the removalof such heat by theI use of oil as a heat absorbing and circulatingmedium, and they are very effectively cooled thereby. It has not,however, previously been found practicable to cool rotating machinery bythe use Aof oil, since submergence in oil produces prohibitive losses ofenergy through the churning of oil by the rotating parts, and the use ofoil circulated through enclosed pipes has not been successful because ofthe complicated and bulky tubes and conduits required. Although someattempt has been made to prevent or minimize the loss of energy due tochurning of oil, (which loss not only detracts from mechanicalefficiency but represents a conversion of such energy into heat) byenclosing the rotor in a cylinder of non-magnetic material, thecirculation of oil is thereby so interfered with as to make the coolingsystem ineffective. Accordingly, vin actual practice, as for as I amaware, only the gaseous fluids have been used for the cooling ofrotatingy dynamo-electric machinery, air being the preferred fiuidbecause of the common occurrence thereof-and ease with which it isobtained.

My invention provides means for the utilil propriate portion of themachine. By the device of my invention I am enabled to utilize thedesirably high cooling capacity of oil for the cooling of rotatingmachinery without the introduction of bulky conduits, Iand without theproduction of large energy losses from churning of the fluid. I am thusenabled to obtain a substantial and important increase in continuousrating of a dynamo-electric machine, and accordingly a greatly improvedperformance and a lower cost of production, from which follows areduction in the cost of operation in the handling of electric energy.'

Other objects and structural details of my invention will be apparentfrom the following description when read in connection with theaccompanying drawings, wherein:

Fig. 1 is a sectional view in vertical elevation of an embodiment of thedevice of my invention;

Fig. 2",.is a side view in vertical elevation of the same embodiment;

Fig. 3 is a sectional 'view in vertical eleva- .tion of an alternativeembodiment;

Fig. 4 is a sectional view in vertical elevation of a second alternativeembodiment, and

Fig. 5 is a side View in vertical elevation, partly in section, of theembodiment of Fig. 4.

It is well known that oil has a very much higher specific heat than air,and that aecordingly the cooling effect which can be obtained from it ismuch greater. For instance, oil has a weight of about pounds per cubicfootswhile air has a Weight of about 0.08 pounds per cubic foot. Thespecific heat/ofY oil is about 0.5, Where that of airis about 0.237. Theratio of heat absorbing capacity of equal volumes of air and 'of oil isthen given by the following equation or about 1450 times.

used. The oil is preferably applied in the form of a spray, or mist, orin relatively small drops, so that a minimum of churning effect isproduced in the mixture by the movement of the rotor, andso that nosingle particle is suiciently large to produce unduly large impactforces when it is thrownfrom the moving rotor to the stator. The sprayis formed at the outer face of the rotor. The cooling liquid isconducted to a receptacle at or' near `the periphery of the rotor whereit collects in the form of aliquid in substantial quantities and thusdevelops the maximum centrifugal force, escaping therefrom through smallopenings as a spray yagainst the opposing face of the stator. Therotation of the rotor itself within the spray is thereby avoided.Another advantage of this arrangement is the fact that the centrifugalforce developed in the liquid can be utilized to induce the circulationof the cooling liquid through a closed system.

vTo prevent loss of oil, the circulating medium should be enclosed. Thedynamo-electric machine may be provided with closed -end plates andframe with a receiver portion, and drain, at the bottom, so that as theoil spray strikes the stator, it may drain down over the hot surfaces ofIthe machine to the receiver, after which it may be cooled andrecirculated. The mixture of liquid and gas may consist of a fluid, suchas oil, and air, or 'it may preferably consist of a less Hammablemixture. For this purpose, it may consist of a mixture of oil spray andcarbondioxide, with or without the inclusion of a small roportion ofair, or .it may consist of a mixture of oil and nitrogen, also with orwithout the inclusion of small quantities of air, insuiicient to producea combusti le mixture with the oil. 'f`- A preferred embodiment of thedevice of my invention is shown in Figs. 1 andl 2. These figures showthe essential parts of la typical dynamo-electric machine to which theimprovement of my -inventionfmay be advantageously applied. The machinemay consist of a shaft, 1, supported in bearings, to which is attached arotor 2. The rotor may be a rotating fieldmor a rotating armature, asdesired. In the embodiment shown, it is indicated as a rotating fieldhaving salient poles, with appropriate field windings 4 thereon. ATherotor is surrounded by a stator 5, which may consist of laminations 6,having windings 7 positioned in ap ropriate slots therein. Passages 8,for coollng iiuid, are provided through the body of the statorlaminations. A suitable frame member 9 is provided for the support ofthe laminations formingpthe stator, and appropriate end-bell i closuremembers 11 and 12 are likewise provided, making a close fit about theshaft 1 and against the machine frame 9.` The rotor also has fan blades,as shown, for causinga circulation of the air or-other gas containedinthe housing 11, 12, of the machine. A clo sure member 14 is providedat the bottom of the frame 9 to form a receptacle for the cooling fluidcollecting there. A drain pipe 15' is rovided, connected thereto, andled to a storage reservolr 16.

.A circulating pump 17 is provided with p the suction inlet connected tothe reservoir 16. The shaft 1 is desirably provided with a passageway orduct 18 extending from one end to a point within the hub of the rotor 2,and connection is made at that point by a plurality of radial ducts 19extending toward the surface of the rotor. At the rotor surface andbetween the salient poles of a plurality of liquid receptacles formingspray heads'21are provided and connected to the radial channels 19,'thechannel 18, and the poles. Either construction provides a cur-L rent ofiuid consisting partly of gas and partly of sprayed oil. The spray heads21- may desirably be of a pattern to provide aV plurality of sprays ofoil separated axially by a distance equal to the axial separation of theVentilating ducts 8 in thestator.

, The current of fluidL from the spray heads 21 on the rotor isdirectedtowards the inner surface of the stator inthe bore thereof, and towardsthe inner openings of the Ventilating passages therethrough. The greatlyin creased thermal. capacity of this fluid, as compared to air alone, isthus available for the cooling both of the rotor member and the statormember. A portion of the oil may be conveyed through the Ventilatingchannels 8 in the stator body'in the form of a spray and collect asubstantial amount of heat therefrom, either by radiation or byconduction. It 'is desirable that the spray heads 21 be so positionedthat the openings 22 through which the oil is discharged and sprayed arelocated in the planes of the Ventilating ducts 8, in order to dischargeas large a portion of the oil through the Ventilating yducts aspossible, and to minimize the accumulationv of iuid oil within the airgap between the rotor and stator. Accordingly While some o f the oilspray is carried freely through the lducts 8, other portions may strikethe surfaces of the Ventilating ducts, and coalesce thereon into a layerof liquid. This layer may be carried radially outward along the surfacesof the Ventilating ducts by the current of mixed air and oil spray. Inits passage over these surfaces, the oil layer is advantageously relatedthereto for the desired cooling effect, and it is enabled to absorb asubstantial amount'of heat in the course of the flow. The oil is thuscarried to the outersurface of the stator, through the Ventilatingducts, and it then flows downward to the receptacle 14 at the bottom ofthe frame, from 'which location it is conveyed by the pipe 15 to thecooler and reservoir 16 where the absorbed heat is removed anddissipated. The oil is then recirculated by the pump 17 to pass throughthe cycle again for the collection of further quantities of heat. Bythis means a very thorough and effective cooling of the dynamo machineis obtained with the handling of a minimum bulk of cooling fluid.

It' is not essential that the cooling liquid be conveyed to the rotorthrough an opening in the shaft. It may equally well be conveyed byother means, such as that shown in Fig. 3, where the oil leaves the pump17 and is conveyed to conductors 23, which discharge the cooling oilinto troughs 24 forming liquid receptacles and located at points nearthe periphery of the rotor. It is collected from the stationaryconductors 23 which lead to the troughs 24, and is held against theframe of the rotor by centrifugal force. This construction isparticularly advantageous in the case of the well known squirrel cagetype of motor, in which the rotor consists of lami nations 25 havingperipheral slots in which are positioned the inductor bars 26characteristic of this type of machine. rl`he oil may be conductedthrough suitable channels v 27 in the rotor body from the troughs 24 toleo the rotor surface. at which point -it maybe -sprayed by anyappropriate means, which may consist of jet plugs or other spray devicespositioned within and near the outer ends of the channels 27. Thestatorcrrstruction may desirably be similar to that-indicated in Fig. 1,and may consist of laminations 6 having Ventilating ducts 8therethrough, supported by a frame member 9 with end-bell members 11 and12, a-bottom receptacle or reservoir 14, a drain pipe 15, and cooler andstorage tank or reservoir 16. The oil is then discharged by the pump 17through the pipes 23 into the-troughs 24 from which it passes throughthe ducts 27 and is sprayed thereby. The ends of the ducts 27 aredesirably positioned in the plane of the Ventilating ducts 8, aspreviously described, and the oil spray, together with a portion of gasas previously" described, is dischargedinto them for the production of asimilar cooling effect upon the structures. The cooling oil flows overthe warm surfaces collecting heat and is caught in a receptacle orreservoir 14 at the bottoni of the frame member, from-which it isconveyed lto a cooler, and storage tank, and thereafter 1s recirculatedas before.

By this construction usually effective and eflicient cooling means areprovided for the induction type of motor, whereby much superior coolingeffects, and therefore much higher load capacity, are obtainable from ap given construction.

For certain typesof machines it is not, however, necessary that acirculating pump be provided for the handling of the oil fiuid. Instead,suitable scoops and channels may be provided upon the rotor, dippinginto a supply of oil fluid at the bottom of the case and frame, toconvey the cooling oil to the rotor. These may consist of curved scoops,

or pipes 28, as shown in Figs. 4 and 5, fas` tened to the rotor 29, andrevolving with 1t. As cach scoop revolves, it strikes the pool of oil 30at the bottom and some of the oil passes into the scoop, to bedeliveredto the annular trough 31 upon the rotor 29 from whichl it isdelivered by suitable ducts 32 to spray heads as before. It is thensprayed therefrom into and against the stator 5 and the Ventilatingducts 8 therein, Where it acts,

as previously-described, for the removal ot'l cooling as that obtainedby air, by the use of very much .smaller Ventilating ducts, or

"if the maximum size of Ventilating ducts are employed it is possible toproducev much more effective cooling. The device of my construction thusmakes it possible to increase the duty on dynamo-electric machinery,thereby considerably reducing .the cost of machinery for a given poweroutput,since the additional parts required for the application of thedevice of my invention are very small items, in the cost of themachinery. Thus a direct reduction of the cost of electric power isprovided.

Further advantages of the device ofmy invention are found in the factthat the cooli ing system may be made completely closed,

recirculatinga given fluid as it is needed. Thus no external air need besupplied, and the conveyors and ducts which would be necessary for suchsupply, are saved. Like- Wise the elimination of the need for coolingair reduces the amount of dirt and moisture which would otherwise becarried into the machine by such circulating air. In consequence, theinsulation condition of the machine is much improved, and the necessityfor frequent cleaning to remove dirt and other obnoxious material isavoided. The presence of the oil directly adds to the insulationresistance, because of its own high Vinsulation value and Abecause ofthe elimination of moisture. Likewise the system makes is possible toenclose the machine in a noneombustible atmosphere, thereby greatlyreducing the hazard of lires which may occur in the insulation due tooverload, excess voltage, and `other factors which tend to injure theinsulation. Likewise in the event that fire occurs in the insulation, itis smothered at once upon the removal of load from the machine, by thecooling effect of the large quantities of oil thrown in, and by the lackof oxygen to supportcombustion.

The device of my invention 1s particularly applicable to relativelylarge dynamo maV chines, such as generators, rotry converters, and largemotors. It is, however, equally well adapted to application to thesmaller types of industrial motors, and is also applicable to railwayand other transportation motors. In such service it is particularlyadvantageous because when so equipped, the

motors are operating in a medium having a very high insulationresistance, as compared to operation under ordinary conditions wherethey are in a medium charged with moisture and other matter, tendingtowards a low insulation resistance.

While I have shown but three embodiments of my invention in thepreceding description, they are capable of various modiicationstherefrom without departing from the spirit thereof, and it is desired,therefore, that only such limitations shallbe placed thereon as arerequired by the prior art or indicated by the appended claims.

I claim as my invention: 1. In a dynamo electric machine, comprisingrotor and stator., means for spraying the interior surface of the statorat a series of points along the length of its air gap with oil.

and simultaneously directing gas currents against said surface, andmeans for recovering and. recirculating said oil.

2. In .a dynamo-electric machine, a rotor member and a stator member,the rotor having an internal circumferential trough within and near itsperiphery, openings extending through the trough in an outward directionand means v,for .circulating a cooling liquid in a closed path includingsaid trough, anda stationary liquid feeding pipe extending over the openinner periphery of said trough. a

3. In a dynamo-electric machine, a rotor member and a stator member, therotor having an internal circumferential trough within and near itsperiphery, openings extending through the 'trough in an outwarddirection and means for circulating a cooling liquid in a closed pathincluding said trough, said means comprising a collecting reservoirbelow the axis of the rotor and a scoop rigid with the rotor andextending into the reservoir.

4. In a dynamo-electric machine, a stator,

, anl internal rotor facing the stator and having gas upon the stator inconjunction with said liquid spray.

5. In a dynamo-'electric machine, a cooling systemu com rising a stator,an internal vrotor facing the stator, as housing enclosing the same, areservoir for holding a cooling liquid within the housing, means carriedby the rotor for continuously removing liquid from the "reservoir andsupplying it to the interior of the rotor, and spray means on the outerperiphery of the rotor for' discharging liquid in spray form into theair gapof the machine.

6. In a dynamo-electric machine, a cooling system comprising a statorhaving radial passages therethrough, an internal rotor facing the statorand having a liquid receptacle at its outer face, a. housing enclosingthe rotor and stator and providing a reservoir for holding a. codlingliquid below the stator, means carried by the rotor and dipping into thereservoir for continuously removing liquid from the reservoir andsupplying it to the said receptacle., and spray means on the outerperiphery et the rotor for discharging liquid in spray form into the airgap of the machine. 7. In a dynamo-electric machine, a cooling systemcomprising a stator having radial passages therethrough,A an internalrotor facing the stator andhaving a liquid receptacle at its outer face,a housing enclosing the rotor and stator and providing a reservoir forholding a cooling liquid below the stator, means carried by the rotorfor continuously removing liquid from the reservoir and supplying it tothe said receptacle, spray means on the outer periphery of the rotor fordischar ing liquid in spray form into the air gap o the machine, andmeans for circulating a current ofraswithin thehousing coincident withthe rota ion of the rotor.

8. The method of cooling an electric translating device comprising rotorand stator cores and windings which consists in continuously subjectingthe exterior ot the rotor and interior ofthe stator in the air' gap ofthe machine to the cooling effect of a liquid'spray,

my signature.

` FRANK G. BAUM.

